The overall objective of this application is to continue the development and characterization of clonal lines of rainbow trout (Oncorhynchus mykiss) as models for biomedical research. Tasks of the present project will be divided between two laboratories: Dr. Gary Thorgaard's laboratory in the Department of Zoology, WSU, and Dr. Sandra Ristow's Laboratory in the Department of Animal Sciences, WSU. Lines of trout will be propagated and developmentally and behaviorally characterized by Dr. Gary Thorgaard's laboratory, and they will be immunologically characterized by Dr. Sandra Ristow's laboratory. The Specific Aims of the joint project are: 1) propagate and disseminate these trout as biomedical models; 2) examine developmental characteristics (development rate at three different temperatures, several meristic characters, and three measures of smoltification) in five clonal lines of rainbow trout; 3) examine behavioral and stress responses in five clonal lines of rainbow trout; 4) more fully characterize the T-cell like compartment and the natural cytotoxic cell activity of the lines of trout by completing the establishment of syngeneic cell lines, more fully characterize mixed lymphocyte cultures between the lines, graft across allogeneic lines, and examine natural cytotoxic cell (NCC) activity in the anterior kidneys of the trout; and 5) clone and sequence the following molecules that are trout analogues of the important T-cell function molecules of murine immune system: the major histocompatibility I molecule (MHCI), the beta chain of the putative T-cell receptor, and beta 2 microglobulin in the five clonal lines of trout.